The present invention relates to a method for reprocessing a dialyzer for hemodialysis, and more particularly, to a method for reprocessing a dialyzer by cleaning the dialyzer for reuse. This invention also concerns with a reprocessing apparatus for carrying out said method for reprocessing a dialyzer.
Reuse of dialyzers for hemodialysis is prohibited by law in Japan in order to prevent infection or the like. However, reuse of dialyzers is allowed in the U.S., People""s Republic of China, parts of Europe and other countries, wherein it is allowed, above all, to use the same dialyzer for the same patient a number of times.
For example, in the U.S., reusing dialyzers is beneficial in terms of cost savings for a dialysis center (unit) from the viewpoint of insurance system. Dialyzer reuse grew rapidly during the 1980s. Currently at least 75% of dialysis centers (units) is reusing dialyzers.
Between 1980 and 1992, the mean number of uses is 10 to 14 according to statistics.
Generally, regarding the dialyzer with which hemodialysis has been carried out, its blood compartment (space inside of hollow fiber membranes in the case of a hollow fiber dialyzer) is partly clogged, or blood components such as blood cells, platelets and proteins are deposited on the membrane surface. Further, a dialysate compartment (space inside of a housing holding the hollow fiber membranes in the case of a hollow fiber dialyzer) is contaminated with bacteria, endotoxins and the like derived from the dialysate used.
Consequently, for reuse of such dialyzer, it is necessary to clean the dialyzer with a cleaning disinfectant after dialysis treatment. In the U.S., formaldehyde, acetic acid-peracetic acid-hydrogen peroxide mixtures, glutaraldehyde and the like are used as the cleaning disinfectant.
It is said that the reprocessing procedure can improve the biocompatibility, particularly regarding cellulosic semipermeable membrane type dialyzers which are currently in wide use. That is to say, new cellulosic dialyzers, when used, are likely to cause problems such as leukopenia, hypoxemia, amyloidosis and syndromes which make dialysis difficult, e.g. nausea, vomiting, itching or hypotension due to activation of complement. However, these problems are reportedly alleviated progressively while the dialyzer after dialysis treatment is reused by being cleaned with a germicide, although there is a report demonstrating that such symptoms were not reduced by dialysis with reprocessed cellulose acetate hollow fiber dialyzers.
Despite the potential benefits of dialyzer reuse outlined above, dialyzer reuse may involve risks. Now concerns have arisen regarding its potential long term hazards.
These hazards include, for example, ineffective dialysis because of a poorly functioning dialyzer resulting from degradation of membrane performance, risk of infection due to inadequate sterilization, and influence of long-term exposure to disinfectants.
Especially, with a cellulosic dialyzer, the cleaning disinfectant used for reprocessing deteriorates dialysis membranes and reduces the dialysis function, occasionally resulting in unsatisfactory dialysis treatment.
One of the greatest potential hazards in reuse is the risk of microbial infection due to inadequate sterilization of the dialyzer. Owing to the degradation or damage of dialysis membranes repeatedly exposed to germicides, bacteria may be permitted to pass from the dialysate compartment into the blood compartment, and a patient may be contaminated with toxins such as endotoxins.
Furthermore, there is an adverse influence of a small amount of residual germicide which has not been removed by cleaning in the reprocessing procedure. For example, regarding formaldehyde conventionally used as a germicide for reuse, there is a high incidence of an antibody to blood group N (anti-N like antibody) which resulted in enhanced hemolysis and destruction of kidney grafts. Such immune mechanisms stimulated by formaldehyde exposure which are responsible for hemolysis are induced in patients exposed to formaldehyde concentrations even as low as 2 ppm. Studies in animal species have shown that formaldehyde is carcinogenic.
Consequently, formaldehyde should be completely removed by rinsing. For this purpose, it is necessary to carry out a prolonged expensive rinsing step using a large amount of water. However, the complete removal is substantially impossible from the viewpoints of costs and efficiency.
It is an object of the present invention to provide a method for reprocessing a dialyzer for reuse, which can minimize the reduction in dialysis function due to degradation or damage of the dialyzer, and which uses a safe cleaning disinfectant.
It is another object of the invention is to provide a reprocessing apparatus for carrying out the foregoing reprocessing method.
The present inventors conducted extensive research to achieve these objects, and found that the objects can be achieved when a dialyzer is cleaned for reuse by using electrolyzed strongly acidic water alone as the cleaning disinfectant, or by carrying out cleaning with electrolyzed strongly alkaline water and cleaning with electrolyzed strongly acidic water, with a rinsing step with water being conducted therebetween. The present invention was completed based on this novel finding.
Thus, the present invention provides a method for reprocessing a dialyzer for hemodialysis, the method comprising the steps of rinsing with water (preferably reverse osmosis processed water) a blood compartment and a dialysate compartment of the dialyzer used for dialysis treatment, and cleaning the compartments with electrolyzed strongly acidic water.
The present invention also provides a method for reprocessing a dialyzer for hemodialysis, the method comprising the steps of rinsing with water (preferably reverse osmosis processed water) a blood compartment and a dialysate compartment of the dialyzer used for dialysis treatment, cleaning the compartments with electrolyzed strongly alkaline water, rinsing the compartments with water (preferably reverse osmosis processed water) and cleaning the compartments with electrolyzed strongly acidic water.
Furthermore, the invention also provides an apparatus for cleaning and disinfecting a hemodialysis dialyzer for reprocessing (reprocessing apparatus), the apparatus comprising:
(a) a tank for holding electrolyzed strongly alkaline water,
(b) a tank for holding electrolyzed strongly acidic water,
(c) a tank for holding water,
(d) two pumps,
(e) lines extending from the above three tanks and connected to respective inlets of the two pumps,
(f) valves disposed in the respective lines mentioned in (e) upstream of the pumps,
(g) a line which removably connects an outlet of one of the two pumps to a dialysate inlet port of the dialyzer to be cleaned or to a dialysate outlet port thereof,
(h) a line which removably connects an outlet of the other of the two pumps to a blood inlet port of the dialyzer to be cleaned or to a blood outlet port thereof,
(i) a line removably connected to the blood inlet port of the dialyzer or to the blood outlet port thereof, the line being disposed for the discharge of the water, electrolyzed strongly alkaline water or electrolyzed strongly acidic water flowing out from the blood compartment of the dialyzer, and
(j) a line removably connected to the dialysate inlet port of the dialyzer or to the dialysate outlet port thereof, the line being disposed for the discharge of the water, electrolyzed strongly alkaline water or electrolyzed strongly acidic water flowing out from the dialysate compartment of the dialyzer.
If desired, the above apparatus further comprises:
(k) a first discharge line connected to the downstream terminal end of the line as defined in (i) for the discharge of the water, electrolyzed strongly alkaline water or electrolyzed strongly acidic water flowing out from the blood compartment,
(l) a line branching out from the first discharge line,
(m) a second discharge line connected to the downstream terminal end of the line as defined in (j) for the discharge of the water, electrolyzed strongly alkaline water or electrolyzed strongly acidic water flowing out from the dialysate compartment, and
(n) a line branching out from the second discharge line,
wherein a valve is disposed in each of the line (l) branching out from the first discharge line and the line (n) branching out from the second discharge line.
In this case, the membrane pores can be cleaned by opening or closing said valves, i.e. by conducting the so-called reverse filtration.
Further, an electrolyzed water generator may be connected to the above apparatus of the present invention, and can be used as a component of the apparatus. In this case, the apparatus further comprises a line connecting the water tank to a water supply port of the electrolyzed water generator, a line connecting a discharge port for electrolyzed strongly acidic water of the generator to the tank for holding electrolyzed strongly acidic water, and a line connecting a discharge port for electrolyzed strongly alkaline water of the generator to the tank for holding electrolyzed strongly alkaline water.
As compared with conventional methods using formalin, the method of the invention employs electrolyzed strongly alkaline water and electrolyzed strongly acidic water which are non-toxic and non-hazardous, and therefore assures safety. Further, the degree of degradation of the dialysis membrane is mitigated, and it is sufficient to use a small amount of water for rinsing.